London, May 13 : A new study has revealed that although beta-blocker drugs might help prevent heart attacks during surgery, they do have a possibility of increasing the risk of death and major stroke.
The findings are based on POISE, the world's largest randomised trial addressing perioperative cardiac complications.
The trial evaluated the effects of a beta-blocker versus placebo given to patients around the time of surgery.
"POISE demonstrates that a beta-blocker given around the time of surgery decreases a patient's risk of a heart attack but increases their risk of a major stroke and death," The Lancet quoted Dr. P.J. Devereaux, POISE co-principle investigator, McMaster University, Hamilton, Canada, as saying.
Surgery boosts patients' catecholamines, or stress hormones, which increase the heart's requirement for oxygen.
And stress on the heart can cause serious events such as a heart attack.
Since beta-blockers reduce the effects of increased catecholamines some doctors thought that they might prevent serious heart complications around the time of surgery.
"Initial small trials suggested beta-blockers were beneficial around the time of surgery but more recent moderate sized trials did not show any benefit. We undertook POISE to provide a clearer understanding of the effects of a beta-blocker around the time of surgery," Dr. Homer Yang, POISE co-principal investigator, University of Ottawa, Ottawa, Canada. Dr. Salim Yusuf, POISE steering committee chair, McMaster University, Hamilton, Canada, said: "A major accomplishment of POISE was that anesthesiologists, cardiologists, internists, and surgeons at 190 centres in 23 countries came together and randomised 8,351 patients - more than 4 times as many patients than all the previous perioperative beta-blocker trials combined. Such efforts are rare, but essential in order to make progress in the management of these patients."
In the trial, researchers randomised 4,174 patients to receive extended-release metoprolol succinate and 4,177 patients to receive placebo starting two to four hours before surgery and continuing for 30 days after surgery.
They found that fewer patients in the metoprolol group (176) than in the placebo group (239) suffered a heart attack, indicating that patients receiving metoprolol were 27 percent less likely to suffer a heart attack.
However, the trial also showed that 29 metoprolol patients as compared to 97 placebo patients died, indicating that patients receiving metoprolol were 33 percent more likely to die.
Researchers also found that 41 metoprolol patients versus 19 placebo patients suffered a stroke, indicating that patients receiving metoprolol had more than double the risk of a stroke.
Considering the heart attacks less than one-third of these patients also had a complication of their heart attack like heart failure.
On contrary, more than half of the patients who suffered a stroke were left incapacitated or needing help with everyday activities.
Analysis of the data suggested that metoprolol increased the risk of death and stroke by increasing the risk of the low blood pressures that required treatment.
"Considering these results, patients are unlikely to accept the risks associated with perioperative metoprolol seen in POISE," said Dr. Gordon Guyatt, POISE outcome adjudication committee chair, McMaster University, Hamilton, Canada.
The study will be published online by the prestigious medical journal, The Lancet.